1. Field of the Invention
The present invention relates to an air intake device for an internal combustion engine and, particularly, relates to an air intake device having an air cleaner and other parts related to the air intake devices combined in a unit.
2. Description of Related Art
Air intake devices for internal combustion engines are disclosed in Japanese Patent Unexamined Publications Hei 6-81735 and Hei 7-83132. Each of the above publications discloses an air intake device in which an intake manifold and an air cleaner are combined into a unit, and fuel injectors, an engine control circuit and a throttle are installed in the unit before the unit is mounted on an internal combustion engine.
European Patent Unexamined Publication 0523027A2 proposes also a unit in which an air cleaner, a throttle and an intake manifold are combined, and the injectors are disposed in the dusty side of the air cleaner.
However, each of the air cleaners disclosed in the above publications is disposed on the top of the unit, and an intake air passage which connects the air cleaner to the throttle is disposed under the air cleaner. As a result, if water gets into the filter element of the cleaner, it passes the filter element and reaches the throttle. In addition, when the element is removed for some reason such as service or inspection, dust may fall to a clean-side portion of the air cleaner and reach the throttle.
Injectors and/or an engine control circuit disposed in the intake air passage are subject to dust or other foreign particles produced from mixture of fuel, water and dust, thereby resulting in shortening life of the engine.
Further, conventional air-intake devices including the above-mentioned devices have spiral intake passages in order to tune the intake air characteristics to respective engines. It is, however, difficult to provide such complicated spiral air intake passages by molding from resinous material.